Prior workers in the art during the past several years have developed numerous types of more or less automatically operating bicycle transmissions. The prior art transmissions have generally been designed to automatically vary the gear ratio between the input and the output in response to the effort exerted upon the pedals by the user. For example, U.S. Pat. No. 3,850,044 to Hagen and U.S. Pat. No. 3,969,948 to Pipenhagen, Jr., are exemplary of previous types of automatic bicycle transmissions wherein the positions of a plurality of chain contacting and driving sprockets can be automatically varied between radially inward positions and radially outward positions to thereby automatically vary the effective diameter of a sprocket wheel assembly. The determination of the radial positions of the various driving sprockets in these transmissions is a function of the input torque whereby, by increasing the input torque, the effective diameter of the sprocket wheel assembly components will be decreased to correspondingly increase the power output of the transmission. When the input torque applied at the pedals is increased, the plurality of chain contacting sprockets would be urged in a direction to increase the effective diameter of the chain driving sprockets, thereby decreasing the output torque, but increasing speed.
Other types of automatic bicycle transmissions have been disclosed in may previous Patent Cooperation Treaty applications, International Application Nos. PCT/US82/01271 and PCT/US83/0089.
All of the prior art automatic bicycle transmissions of which I am familiar suffer from a common operating problem whereby the interaction of the driving chain with the circularly spaced driving sprockets is such that an increase or decrease in the effective diameter of the sprocket wheel assembly could not be smoothly made without a noticeable change. The disengagement and engagement of the individual driving sprockets and the driving chain was in the past always accompanies by an unwanted and uncontrollable clatter or shock, a condition which was detrimental and annoying when operating any type of bicycle transmission. In the case of my more recent inventions, as disclosed in the said Patent Cooperation Treaty applications, the problems of clatter or shock had largely been solved, but the changes in effective sprocket wheel assembly diameter were still accompanied by an undesirable drag or "feel". While my previous automatic transmissions provided a considerable improvement over everything that was previously known in this field, nevertheless, there was still a noticeable lack of smoothness which could be of concern to the user.
Additionally, the prior art automatic transmission of which I am aware have tended to be quite complicated and cumbersome in construction, thereby resulting in increased manufacturing costs, in increased maintenance costs, in increased weight and in interacting components that were continually subject to breakdown or wear.